This article explains the "Invalid sequence value" warning that can occur for individual calendar events when migrating to Google Workspace. This is a non-critical warning indicating an event was not updated.
1. Symptom
During a migration to Google Workspace, you notice warnings for specific calendar appointments in the migration logs. The warning message is similar to the following:
[GoogleCalendarV3Importer] [Warn] [user@example.com] Appointment: 'Team Meeting' failed: Invalid sequence value. The specified sequence number is below the current sequence number of the resource. Re-fetch the resource and use its sequence number on the following request.
This warning means that CloudM Migrate attempted to create or update a calendar event, but Google rejected the change because a newer version of that same event already exists in the destination calendar.
2. Cause
Google Calendar uses an internal versioning system for each event, known as a "sequence number." Every time an event is modified (e.g., its time, description, or attendee list changes), the sequence number increases.
The "Invalid sequence value" warning occurs when CloudM Migrate tries to write an event with a sequence number that is lower than the one already stored in the destination calendar. This happens in two common scenarios:
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Pre-existing Events: The user being migrated was already an attendee on an event invitation sent from another source user. The event was therefore already in their destination calendar before the migration even started.
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Delta Migrations: You are running a second (or subsequent) migration pass. An event was migrated in the first pass, but was then updated directly in the source and the destination. If the destination event was updated more recently, its sequence number will be higher, and Google will reject the update from the migration tool.
In essence, Google is protecting the user's calendar from being overwritten with an older version of an event.
3. Resolution
Since this is a warning, it does not stop the user's migration from completing. How you proceed depends on whether you need to force an overwrite of the events.
Option 1: Acknowledge the Warning (Recommended)
In most cases, no action is required. The warning simply confirms that the event already exists in the destination calendar, which is often the desired outcome. You can safely ignore these warnings, knowing the user has a version of the event in their calendar.
Option 2: Force re-migration of Events
If you are certain that the source events must overwrite the destination events (e.g., during a delta migration where source changes are definitive), you must manually remove the existing events from the destination before remigrating.
Warning: This process is destructive and will permanently delete the existing events from the destination user's calendar.
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Identify Failed Events: Review the migration logs in CloudM Migrate to identify which user(s) and which specific events are producing the warnings.
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Delete Events in Destination: Log in to the destination user's Google Calendar account and manually delete the specific events that are causing the warnings.
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Clear Migration History: In the CloudM Migrate user interface, select the affected user(s) and use the action to clear the migration history for Calendar items. This makes the tool "forget" it has already migrated these events.
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Re-run Migration: Start a new migration pass for the affected user(s). With the conflicting events gone and the history cleared, CloudM Migrate will now create new events in the destination calendar using the data from the source.